Array antenna for receiving radio communication

Details Array antenna for receiving radio communication Array antenna for receiving radio communication

1992-12-02

1994-11-22

Hajec, Donald

Communications: radio wave antennas

Antennas

With coupling network or impedance in the leadin

343754, H01Q 2100

Patent

active

053673131

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

1. Technical Field
The present invention relates to an array antenna for receiving a signal in a microwave band.
2. Background Art
FIG. 2 shows a conventional array antenna for receiving radio communication. In FIG. 2, the reference numeral 1 represents a radiating element, 2 a feeder for combining the radio waves which are received by the radiating elements 1, 3 a low noise amplifier (LNA) and 4 a frequency converter.
The operation of the conventional array antenna will now be explained. The radio waves received by a plurality of radiating elements 1 are combined by the feeder 2 and amplified by the LNA 3. Thereafter, the frequency of the combined radio wave signal is converted into a signal having predetermined frequency by the frequency converter 4, and the signal is supplied to a receiver (not shown).
The gain over temperature G/T, which is the most important index in a receiving antenna, is a value obtained by dividing the gain G of the antenna by the noise temperature T of the whole array antenna for receiving radio communication. In the structure shown in FIG. 2, the noise temperature T of the whole array antenna for receiving radio communication observed at the radiating elements 1 is obtained from the following formula (1):
L : the loss of the feeder 2
T.sub.0 : environmental temperature
T.sub.e : the equivalent input noise temperature of the LNA 3
T.sub.c : the equivalent input noise temperature of the frequency converter 4
G.sub.1 : the gain of the LNA 3
In the conventional array antenna for receiving radio communication having the above-described structure, it is possible to enhance the G/T by increasing the antenna directive gain G. In order to increase the antenna directly gain G, however, it is necessary to increase the number of radiating elements 1, which leads to the increase in the length of the wiring in the feeder 2 and, hence, to the increase in the loss L of the feeder 2. Since the increase in the loss L of the feeder 2 gradually deteriorates the G/T, there is a limit to the realizable G/T.


DISCLOSURE OF THE INVENTION

Accordingly, it is an object of the present invention to eliminate the above-described problems in the prior art and to provide an array antenna for receiving radio communication which has an enhanced G/T and which can be realized with the minimum necessary increase in cost.
To achieve this aim, in an array antenna for receiving communication according to the present invention, the antenna is divided into the minimum necessary number of sub arrays and an LNA is added to each sub array. By adding the LNA to each sub array, it is possible to reduce the influence of the loss of the feeder for combining the outputs of the sub arrays, thereby enhancing the G/T. Since it is possible to realize the desired G/T by the minimum necessary number of LNAs, the array antenna is realized at a low cost.


BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the structure of an embodiment of an array antenna for receiving radio communication according to the present invention; and
FIG. 2 is a block diagram of the structure of a conventional array antenna for receiving radio communication.


DETAILED DESCRIPTION

In FIG. 1, the reference numeral 1 represents a radiating element, 2 a feeder A in a sub array, 3 an LNA, 4 a frequency converter, 5 a feeder B provided outside of the sub array, and 6 the sub array.


BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be explained hereinunder with reference to FIG. 1.
In FIG. 1, the reference numeral 1 represents a radiating element, 2 a feeder A in a sub array, 3 an LNA, 4 a frequency converter, and 5 a feeder B for combining the outputs of the sub arrays. This embodiment is characterized by the fact that a single array antenna is composed by N (n: plural number) sub arrays (sub array 1 to sub array N) and that the sub array is composed of a predetermined number of radiating elements 1, and the feeder A 2 and the LNA 3, which are connected in cascade to the radiating elements 1.
In

REFERENCES:
patent: 4791428 (1988-12-01), Anderson
patent: 4965605 (1990-10-01), Chang et al.
patent: 5038151 (1991-08-01), Kaminski
patent: 5218368 (1993-06-01), Huruno et al.
H. Iwasaki, K. Yasukawa, K. Hidaka & T. Morooka, "Analysis of a Microstrip Active Array Antenna for DBS" Mar., 1987, National Convention Record-The Institute of Electronics, Information and Communication Engineers, Part 3.

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